Monomolecular film formers for water surfaces



United States Patent Ofi 3,241,908 Patented Mar. 22, 1966 ice 3,241,908MONOMOLECULAR FiLM FORMERS FOR WATER SURFAfiES Paul A. Mazur, 22Conlrlin Place, Burnout, Ni, and Curtis Michel, 148 E. 48th St, NewYork, NY. N Drawing. Filed P421". 5, 1962, See. No. 177,233 12 Claims.(Cl. 21-4565) This invention relates to the formtaion of monomolecularfilms of polar compounds on water surfaces. More specifically, it dealswith the efficient formation of insoluble monomolecular layers of solidfatty alcohols and similar polar compounds on water surfaces to reduceevaporation loss of water from reservoirs, and the like.

Although, in the past, water has been a cheap commodity, theconservation of which has not been of any consequence, the picturethereof has changed considerably in recent years, so that now, even theloss from evaporation is taken quite seriously. Then, of course, thereis the forced problem of conservation imposed in areas of ambient hightemperature, low humidity and high aerodynamic turbulence, wherein waterlosses created through surface evaporation and evapo-transpiration aregreat enough not to be ignored.

Within the last thirty years it has been definitely established that theevaporation of water from open reservoirs can be reduced considerably bydeposition, on the water surface, of a monomolecular film of a polarcompound, such as, for example, a solid fatty alcohol, e.g., cetylalcohol, stearyl alcohol, and the like.

Various efforts have been made in the past to contol or reduce suchlosses on a commercial scale. For example, slabs or blocks of thefilm-forming compounds, sometimes with an anchor line cast in them, havebeen floated on the water. While such a method appears to be quitesimple, it possesses the great disadvantage in that, on relatively shortexposure, the compounds (e.g., fatty alcohols) lose their ability todisperse into a monomolecular film because of coating of their surfaceswith algae, suspended solid matter, silt, and the like. Another meth-'od involved placing the fatty alcohol, in flake form, in a wire orplastic mesh raft attached to anchored floats. Besides wire and plasticmesh, gauze bags have been used. Unfortunately, the results achievedhave been similar to those heretofore described with solid blocks,resulting in random and discontinuous release of monomolecular film.

Attempts have been made also to employ solid alcohols in bead form forgeneration of more continuous films, but it was found that the beadstended to float too low in the water, so that the area of contact at theinterface was even less than that achieved with the flake form. The samedisadvantages were observed when the fatty alcohol was employed in theform of cast elongated rods.

Since the distribution energy for spreading a compound into amonomolecular film must be derived mainly from difference in surfacetension, it is highly important that the film former be distributed ontop of the water surface as much as possible. In order to achieve thiscondition, the film formers have been applied in solution form,dissolved in liquid solvents, using the drip, spray, or subsurfacerelease techniques. While the solvent does leave a monomolecular film onevaporation, this method entails .the disadvantage of solvent retentionby the alcohol film unless highly volatile (and thus, less practical)solvents, such as petroleum ether, are employed. Unfortunately, use ofsolvents involves many concomitant evils, including toxicity, taste andodor effects on the water, fire hazards, etc., so that they have notbeen considered seriously for commercial installations. It might bementioned, also, that such additives, including surface-active agents,possess the disadvantage of molecular interference so as to impair theproper orientation of the alcohols on the water surface into continuouscompressed monolayers.

A further prior art method resorted to the casting of the solid alcoholon strings or cords which were distributed on the water surface andmerely floated on it. While this procedure was somewhat less wasteful ofalcohol than the other methods described, the film-forming tendency ofthe alcohol was hardly better than with blocks or flakes.

Attempts have been made to spray from airplanes the surface of bodies ofwater with film-forming compounds, but results have not provedsatisfactory because of the inability to maintain a complete cover dueto blowing away of the charge by the wind. Similarly, agriculturaldusting equipment, akin to that used for dusting dry insecticides oncrops, was found unsuitable for intermittent depositions of smalladditions of film-formers necessary to sustain adequate film coverduring normally-windy field conditions.

One prior art technique used a machine mounted on a motor-driven boatand employing a rapidly-revolving brush to which was applied a solidblock of alcohol. Small particles thus chipped off were blown out of themachine through a motor-driven fan. The trouble here was that theparticle size obtained was coarse and of random size, resulting ineificient monomolecular layer formation.

When powdered fatty alcohol, for example, is suspended in water in theform of a dispersion, with or without the aid of a dispersing agent, andis then dripped, sprayed or otherwise applied to the water surface, theprewetting has been found to be objectionable because less surface ismade available at the air/ water interface, whereby formation of themonomolecular film is delayed. Extended wetting makes the formation of aproperly oriented and compressed mono-layer still less likely, whileadded dispersing agents further interfere with the uniformity andevaporation-suppression effectiveness of the film.

Incidentally, another procedure of the prior art involved melting thefatty alcohol which then was sprayed at some distance above the watersurface, whereupon the alcohol solidified and settled upon the watersurface. A particular disadvantage of this method was that the meltingequipment required considerable care in operation, and was of limiteduse in inaccessible areas. Furthermore, sustained storage of fattyalcohols and similar film formers in melted form may increase theformation of degradation products which interfere with the formation ofthe desired film. Also, there are indications that the interior of thesprayed particles does not cool sufficiently to form the preferredsub-alpha crystal phase which spreads spon taneously to form the desiredm-onolayer. The orientation of these film formers, during aging,proceeds from the alpha phase to the sub-alpha phase and then to the etaphase. The desired orientation is in the two latter crystalline phases.

Finally, powdered fatty alcohols have been packaged in polyvinyl alcoholpackets for use on small water storages. Their disadvantage lies in thefact that, as the polyvinyl alcohol dissolves it coats the individualfilm former particles and thus interferes with desired film formation.And, besides, there is no residual fatty alcohol available forreplenishment of the film when it is blown off by the wind.

All of the aforesaid prior art methods have been mentioned to point outthe fact that considerable work has been done in this field. Yet, inspite of this, there has not been developed a commercially-applicableand efiicient film former, or process of producing such a material.

According to the present invention, the aforesaid disadvantages andlimitations have been overcome and the uniform dispersion of the filmformer has been accomplished so as to achieve unbroken continuity ofcompressed film and thus effect maximum evaporation-retard ingefficiency. Furthermore, film former losses have been reduced to aminimum and spreading efficiency has been extended so that an attenuatedrate of deposition will produce maximum reduction in water evaporationloss. Also, use of the present invention enables utilization ofmaterials which heretofore have been considered as having poor spreadingability when applied in large particle size.

According to the present invention, the waxy compounds ordinarlypreferred as film-forming agents, are produced in a foamed form.Specifically, the material is first heated to its melting point andmelted. Then, air or other gas, such as carbon dioxide, nitrogen, etc.,is whipped or beaten into it, and this mixing is continued while thematerial is cooled. The foam thus created is retained in the compound asit cools and hardens, resulting in a solid foamed mass of thin-walledcells, and having a density of about 75% to about 50% or even 30% orless of the original solid material in the unfoamed state at normal orroom temperature. In this foamed condition, the film former may bestored and transported without undesirable deterioration. Also, due tothe fact that it is self-insulating, ambient heat can melt the outersurface of a cake of the material, but the main inner bulk thereof isstill in foamed condition, ready for use.

When it is to be used, the foamed film-forming composition is easilyabraded, e.g., by scraping or grating, or it is comminuted, pulverized,crushed, or the like, to produce a fine powder of very small particlesize. This abraded powder, in abraded form, is very light and it has avery low density, so that it rides high on the surface of the water.Thus, particle surface is increased at the air/Water interface formonolayer generation. Inasmuch as the object of using a film former isto produce an oriented monomolecular film on the Water surface asrapidly as possible for optimum evaporation-suppression, the smaller theparticle size from which such film is formed, the more desirable it is.By applying the film former in this manner without the use of solvents,there is no danger of fire or toxicity. Since no pre-wetting isnecessary, there is no loss of efiiciency or increase in cost due to useof extraneous chemicals. Reversion to an unstable crystalline phase iseliminated, and sintering (as is encountered with pres-powderedmaterials) is not encountered to any appreciable extent.

Although a mixture of n-hexadecanol and n-octadecanol (e.g., a 50%50%mixture of cetyl-stearyl alcohols) is preferred as the film formingmaterial, other compounds may be similarly prepared and used, includingother solid straight chain aliphatic alcohols (e.g., C to C or even Calcohols), acids and esters having from ten to 40 carbon atoms. Similaruse also can be made of resins, such as polyvinyl acetate,styrene-maleic acid copolymers, synthetic ester waxes, and other similarsolid materials.

The foam may be produced by whipping or beating the molten film formerin a vessel equipped with stirring blades, preferably at high speed, thewhipping action being continued while the foam is cooling. Other methodsfor producing the foamed product include bubbling the air or othersuitable gas through the molten material while it is vibrated, aeratingthe material by blowing it through a jet with air or other gas, etc.Another method for producing the foam is to dissolve a normally-gaseousliquid compound (such as butane, propane, nitrous oxide,chloro-fluorohydrocarbons, etc.) under pressure, and then release thepressure. The resulting cooling effect immediately produces a solidfoamed mass of film former. The foamed material may be extruded in rodsor sheets, or it may be cut into blocks, fragments, or the like, or itmay be formed into balls, pellets (which could be crushed by lightpressure), and the like.

4 The following examples will illustrate some of the many phases of thepresent invention:

EXAMPLE 1 Experiments on ponds of 1 to 2 acres in surface areademonstrated the improvements of this means of applying a substancecapable of generating a monomolecular layer. A number of simple floatingrafts served as dispensers, in which a block of foamed cetyl-stearylalcohol, a mixture of approximately 60-70% normal hexadecanol and 3040%normal octadecanol, foamed by melting the alcohols and beating in airwith a high speed stirrer until the solidified alcohol mixture gravitywas only 25% of its normal gravity, was abraded by the action of anabrading screen rubbing against its surface by Wind and wave motion. Theraft dispensers were anchored in the pond in such a manner and locationas to secure adequate film coverage over the ponds surface for theprevailing meteorological conditions. The movement of the abradingscreen against the foamed block caused small particles of thefilm-generating agent to fall to the surface of the water. The presenceof a compressed monomolecular surface film was detected by the use ofstandard indicating piston oils. The rate of application of the foamedmixture was in the order of 0.5 to 2.0 ounces per acre per day, whichwas found sufficient to replenish film losses and maintain anevaporation-retarding monolayer on the pond during periods of winds ofbetween 2 to 18 miles per hour. Comparisons conducted over a six-weekperiod showed a reduction in evaporation of water of beetween 2535%, fortreated ponds, as opposed to untreated ponds under substantially similarconditions, with due allowance for the effects of rain and seepage.

EXAMPLE 2 Experiments on a lake of about 80-100 acres demonstrated theability of a foamed substance to generate a rapidly-spreadingmonomolecular layer. A dispenser consisting of a shredder and a rotaryexhaust fan was attached to the side of a boat. Blocks of foamedcetylstearyl alcohol, a mixture of approximately 60-70% normalhexadecanol and 3040% normal octadecanol (foamed to 30% of normaldensity) fed into the hopper of the dispenser, were comminuted by theaction of the shredder, and the resultant fine particles were blown outby the exhaust fan. The stream of fine particles was directed toward thesurface of the water while the boat was driven on a transverse courseacross the lake of number of times, creating a pattern of parallellayers of discrete particles perpendicular to the prevailing breeze.Within about 20-30 minutes, the particles generated a monomolecular filmwhich had joined to form a continuous layer over the surface of thelake. The following comparisons with conventional solid block and flakeapplications of cetylstearyl alcohol of the same compositiondemonstrated greater effective film-forming abilities of the instantcomminuted foamed product in terms of time or continuity of filmcoverage:

Time in minutes to form detectable compressed Dist-nice in feet frommonolayer single source Ahraded foam Flake Solid block 3-5 2030 60. 7-10-70. 120-180. 16-25 120-180. Exceeding 360. 30%50 Excee ling 3fi0 Do.

We claim:

1. A monomolecular film former for controlling water evaporation fromwater surfaces comprising a solid compound forming an insolublemonomolecular film on a water surface, present in solid foamed conditionand having a density of less than about of the density of the compoundin the unfoamed state.

2. A monomolecular film former for controlling Water evaporation fromwater surfaces comprising a solid normal aliphatic alcohol having atleast carbon atoms and not over 40 carbon atoms, in the foamedcondition, and having a density of less than about 50% of the density ofthe alcohol in the unfoamed state.

3. A monomolecular film former for controlling water evaporation fromwater surfaces comprising a solid normal aliphatic acid having at least10 carbon atoms and not over 40 carbon atoms, in the foamed condition,and having a density of less than about 50% of the density of the acidin the unfoamed state.

4. A monomolecular film former for controlling water evaporation fromwater surfaces comprising a solid normal aliphatic ester having at least10 carbon atoms and not over 40 carbon atoms, in the foamed condition,and having a density of less than about 50% of the density of the esterin the unfoamed state.

5. A monomolecular film former for controlling water evaporation fromWater surfaces comprising an aliphatic alcohol in the C to C range, inthe foamed condition, and having a density of less than about 50% of thedensity of the alcohol in the unfoamed state,

6. A monomolecular film former for controlling water evaporation fromwater surfaces comprising a mixture of cetyl-stearyl alcohols in thefoamed condition and having a density of less than about 50% of thedensity of the mixture in the unfoamed state.

7. The method of producing a film former for control ling waterevaporation from Water surfaces comprising heating a solid insolublemonomolecular film-forming compound at least to its melting point,incorporating gas into the melted compound until it is in the foamedcondition, and cooling the foamed compound to the solid foamed state. v

8. The method of producing a film former for controlling waterevaporation from water surfaces comprising heating a solid insolublemonomolecular film-forming compound at least to its melting point,incorporating gas into the melted compound until the latter reaches afoamed state, and cooling said compound while the incorporatingoperation is continued and until the compound reaches the solid foamedstate. i

9. The method of producing a film former for controlling Waterevaporation from water surfaces comprising heating a solid aliphaticalcohol at least to its melting point, incorporating gas into the meltedalcohol until it is in the foamed condition with a normal density of notover about of that of the unfoamed alcohol, and cooling the foamedalcohol to the solid foamed state.

10. The method of forming an efiicient monomolecularevaporation-reducing film over a water surface for controlling waterevaporation from said surface comprising forming a foamed mass of solidinsoluble monomolecular film former, abrading said mass to form a finepowder, and scattering said powder over a water surface.

11. The method of forming an efiicient monomolecularevaporation-reducing film over a water surface for controlling waterevaporation from said surface comprising abrading a foamed solid alcoholmass into a powder and strewing said powder over a water surface.

12. The method of forming an eflicient monomolecularevaporation-reducing film over a water surface for con trolling waterevaporation from said surface comprising heating a solid aliphaticalcohol to at least its melting temperature, incorporating gas into themelted alcohol until it acquires a foamed state having a normal densityof not over about 50% of that of the unfoamed alcohol, cooling saidfoamed mass to the solid state, abrading said solid foamed mass into apowder, and strewing said powder over a water surface.

References Cited by the Examiner UNITED STATES PATENTS 1,414,015 4/1922Godfrey 252-368 1,571,625 2/1926 Dawes 252-368 2,200,298 4/ 1939Robinson 260632 2,903,330 9/1959 Dressler 2160.5

OTHER REFERENCES RosanoJournal of Physical Chemistry, volume 60, No. 3,March 1596, pp. 348353.

MORRIS O. WOLK, Primary Examiner.

JOSEPH SCOVRONEK, Examiner.

S. ROSEN, F. W. BROWN, Assistant Examiners.

7. THE METHOD OF PRODUCING A FILM FORMER FOR CONTROLLING WATEREVAPORATION FROM WATER SURFACES COMPRISING HEATING A SOLID INSOLUBLEMONOMOLECULAR FILM-FORMING COMPOUND AT LEAST TO ITS MELTING POINT,INCORPORATING GAS INTO THE MELTED COMPOUND UNTIL IT IS IN THE FOAMEDCONDITION, AND COOLING THE FOAMED COMPOUND TO THE SOLID FOAMED STATE.